Is it possible to have breast cancer at age 17?

Anything...: ...Is possible, but it is extraordinarily unlikely without a known familial syndrome and other first degree (mother, sister) relatives who had breast cancer at a similar age. If you are experiencing symptoms of concern to you, call your doctor.

Yes: Cancer is usually bimodal -- that is young and old, but some people get cancer "in between" in their teens and twenties. While any cancer can happen at any age, some more common in that age group are lymphomas and germ cell tumors (such as testicular cancer).

Rare: I suppose it is possible, but it would be exceedingly rare.

Very rare: The majority of lumps in 17 year old breast will be benign (not cancer). Most women do not develop breast cancer until they are in their 40's or 50's or older. Some women with a very strong family history where other family members got cancer at an early age may get it early too but this is very rare. If concern, talk to your doctor.